1. Field of the Invention
The present invention relates to a heating device, and, more particularly, a heater box to heat polyvinyl chloride(PVC) or similar conduit for the purpose of bending the conduit.
2. Description of the Related Art
Polyvinyl chloride(PVC) pipe is popular for a variety of applications including electrical conduits, pipelines, household plumbing, and utility connections. It is expedient to do bending at a site where the conduit is installed. A portable heating device is therefore needed to accomplish this task. The present invention provides a simple device to economically accomplish this task which is readily transported and hand carried. The related art describes various heater apparatus useful for heating plastic pipe for bending or other shape modifications. The art of interest will be discussed in the order of their perceived relevance to the present invention.
U.S. Pat. No. 5,853,289, issued on Dec. 29, 1998, to Todd et al., describes a gas-supplied pipe heater having a hinged heater box with a gas burner located in the lower portion of the box and a baffle extending along the length of the box and above the burner. The box has accommodation for a plastic pipe inserted for bending to protrude from both ends of the box and to be positioned so as to maintain the inserted pipe above the baffle to avoid direct flame on the pipe. The accommodation is circular cutouts so arranged relative to the box hinge that the box can be placed around a segment of pipe and closed to heat that segment without the necessity of inserting an end of the conduit into the box. The present invention is distinguishable in that it provides spaced supports within the length of the heater box for supporting conduit for heating along the length thereof that extends within the heater box to avoid heated pipe from touching the hot lengthwise baffle through sagging or otherwise. The present invention also employs two lengthwise spaced guides extending along the length of the box and attached to the upper side of the spaced supports so as to allow easy insertion of a plastic conduit through one box end and out the other. These guides may be of any appropriate structure such as solid steel rods or pipes.
U.S. Pat. No. 5,017,760, issued on May 21, 1991 to L. A. Miller, describes an elongated heating device for heating plastic pipe or conduit, having an inner lengthwise pipe wound with an electric heating element, all of which is surrounded by a housing. The present invention is distinguishable in that the housing or box may be opened and closed around the plastic conduit being heated so it is useful in locations where the conduit is already installed and cannot readily be separated into lengths or segments. The present invention is also heated by gas which makes it usable in locations where electricity may not be available.
U.S. Pat. No. 4,437,453, issued on Mar. 20, 1986 to Temple et al., describes a heating device for plastic pipe or conduit and comprises an elongated inner pipe segment surrounded by a manifold which has a "T" portion normal to the manifold, the "T" portion fitting over the exhaust pipe of an internal combustion engine. Plastic pipe or conduit is inserted into an end of the elongated, heated inner pipe segment for heating as desired. The present invention is distinguishable in that the housing or box may be opened and closed around the plastic conduit being heated so it is useful in locations where the conduit is already installed and cannot readily be separated into lengths or segments. Also, proximity to an operating internal combustion engine is not required.
U.S. Pat. No. 3,466,020, issued on Sep. 9, 1988, to C. F. Blinne, describes a plastic pipe heater employing oil or other fuel. The heating chamber is generally cylindrical having an outer casing and an inner tube having truncated conical ends so as to narrow the inner tube at the entrance and exit of the inner tube, thereby providing a loose fit to the outside diameter of the plastic pipe or conduit to be heated. Heated gas is introduced tangentially into the annular volume between the outer casing and inner tube. The inner tube can act as a baffle to protect the plastic pipe from direct contact with the heating gases. The heating chamber has a clamshell type hinged opening means to allow it to be opened to allow the insertion of plastic pipe in the middle of a length thereof. Since the inner tube is in direct contact with heating gases, careful control of heat is necessary to avoid overheating of the plastic pipe. The present invention differs from this apparatus in that the inventive apparatus is much less. complex, being easily portable to a job site for use. There is provision of a baffle and supports therein which keep the plastic conduit to be heated away from the hot baffle, therefore requiring less rigid control of temperature to be effective and avoid damage to conduit being heated. There are guides attached to the supports which assist the insertion of a conduit end through the heater box.
Canadian Patent 1,007,023, issued on Mar. 22, 1977, describes a device for heating and bending plastic pipe, employing heated air for heating the plastic pipe and cooling air or other fluid for cooling the bent plastic pipe. A rotatable heating jacket is employed to provide heat to the plastic pipe in the portion to be bent around a mandrel. Heating or cooling air may be introduced axially into the pipe to accomplish bending or cooling of the bent pipe. The present invention is distinguishable in that the present intention is a much simpler and more transportable device. Use of the present invention is not restricted to bending near the end of a plastic pipe segment but may be used anywhere on a pipe segment or a pipeline to accomplish heating to allow bending in the most practical manner.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus a heater box to bend PVC conduit solving the aforementioned problems is desired.